Abstract
Lactose is the major sugar present in milk and an important osmotic regulator
of lactation. It is digested by intestinal lactase, an enzyme expressed in new-borns.
Its activity declines following weaning. As a result, adult mammals are normally
lactose-intolerant and more than 75% of the human adult population suffers from
lactase deficiency. A reduction in milk lactose content could be beneficial for
nutritional but also agricultural and industrial purposes (less volume to
transport, better milk coagulation, less effluent production). Several attempts
to create transgenic mice producing milk with modified carbohydrate compositions
have recently been described. Depending on whether these modifications resulted
from an alteration of lactose synthesis or from lactose hydrolysis, striking
physiological differences are observed.